1. Field of the Invention
The invention relates to a measuring device, in particular, a vectorial network analyzer.
2. Related Technology
Especially in the context of network analysis, but also with other measurement problems, a component (DUT) to be measured must be excited with a differential signal in the so-called “differential mode”. In the “differential mode”, there is a fixed phase difference of 180° between the two excitation signals. By contrast, in the so-called “common mode”, the two ports of the device under test must be supplied with a precisely in-phase excitation signal. In practice, fixed phase relationships between the excitation signals other than 180° and 0° are conceivable and occur in practice. The measurement problem therefore generally consists in generating two excitation signals, which have precisely the same frequency and provide a fixed, non-fluctuating phase difference relative to one another.
In order to obtain a signal source for the “differential mode”, US 2004/0196051 A1 proposes the use of a common syntheziser for the two excitation ports, wherein the phase differences occurring between the two ports are equalized by control signals, which are supplied to two vectorial modulators disposed directly at the outputs of the signal source. However, the vectorial modulators are relatively expensive components, and this procedure is relatively costly.